1. Field of the Invention
The present invention relates to a device for protecting data stored in a static random access memory (SRAM), and more particularly, to a device for protecting SRAM data including an SRAM data erasing circuit, which erases memory stored in an SRAM at once when illegal separation from a system is detected.
2. Discussion of Related Art
An SRAM is a volatile memory that loses all stored data when power is not supplied due to general characteristics of a RAM. However, when storing important data in an SRAM, a user may protect the data by connecting a separate power switching circuit to the SRAM to continuously supply power.
FIG. 1 is a diagram illustrating an operation of a general power switching circuit.
Referring to FIG. 1, a processor 130 transmits a chip selection signal for reading and writing data from and to an SRAM 120 to a chip selection signal receiving terminal CS_IN of a power switching circuit 110. The power switching circuit 110 then transmits the chip selection signal to a chip selection signal input terminal CS of the SRAM 120 via a chip selection signal sending terminal CS_OUT. The SRAM 120 communicates data with a processor 130 in response to the chip selection signal.
A power input terminal VCC of the SRAM 120 receives electrical power from a power output terminal Vout of the power switching circuit 110. At this point, when an external power supply 140 supplies electrical power, the power switching circuit 110 supplies the electrical power from the external power supply 140 to the power input terminal VCC of the SRAM 120. However, when the external power supply 140 does not supply electrical power, the power switching circuit 110 supplies electrical power to the power input terminal VCC of the SRAM 120 using a back-up battery power supply 150. Accordingly, the power switching circuit 110 may continuously supply electrical power to the SRAM 120 even in circumstances where it is impossible for the external power supply 140 to supply electrical power, and thus the data stored in the SRAM 120 is protected.
Conventional devices for protecting SRAM data using such a power switching circuit can protect data stored in the SRAM by continuously supplying power irrespective of the state of the external power supply. However, when a user with malicious intent separates the attached SRAM from the system, confidential data stored in the SRAM remains in the SRAM after separation and can be accessed.